You depend on your lights to provide you with solid, uninterrupted illumination. So, a flickering light bulb can be annoying, distracting, and even unsafe. Once you trace the cause of the flickering bulb, many solutions are low-cost and simple to implement.
What Causes Light Bulbs to Flicker
With flickering light bulbs, the obvious first step is to retighten the bulb. Over time, even the best light bulbs can slowly unscrew or give way somehow, especially bulbs near areas of vibration. Ceiling light bulbs on first-floor ceilings can be shaken due to foot traffic on the floor above.
Often, the bulb itself does not unscrew—instead, the hot tab in the base of the socket has given way slightly and is not fully making contact, which causes the light to flicker.
Power outlets that service table or floor lamps can cause the bulb to flicker. While the bulb itself may be in good condition, the power source wavers. The cause of this is usually an outlet whose internal metal contact blades have become worn or a loose connection where the wire connects to the outlet.
Faulty Light Fixture
Because they have no moving parts, light fixtures can last for decades. But eventually, time can take a toll on light fixtures as the center hot tab loses tension. Ceiling leaks, foundation shifts, and constant temperature spikes in the attic, too, can affect light fixtures. Also, some light fixtures simply are faulty from the start.
Faulty Dimmer Switch
Dimmer switches are especially prone to causing flickering light bulbs because flickering is how dimmers work. Turning a dimmer up or down isn't like gradually turning a water tap on or off. Instead, a dimmer changes the voltage waveform before it enters the light. It's a flicker that passes so quickly that the eye cannot discern it. Applying more voltage to a dimmer switch than it was designed for is a major cause of dimmer switch failure. Dimmer switches can also fail when a user is trying to dim a CFL or LED bulb that is not intended to dim or when a dimmer made for use with incandescent bulbs is used on a non-incandescent bulb.
Mismatched Dimmer Switch
LED lights are a great advantage to homeowners over earlier incandescents and CFLs due to their bright light, long service life, and cool operation. But when an LED bulb is matched up with a dimmer switch originally designed for use with incandescents, flickering can occur.
Cables lead from the electric service panel (circuit breakers) to the light switch, and along the way anything can go wrong. Cables located in walls are generally not to blame. As long as they were installed with staples or routed through holes in the studs, these electric cables tend to stay in place.
The problem tends to center around connection points where individual wires within the cable sheathing branch out and are attached to devices or in junction boxes.
Lights often are on dedicated light circuits—electric circuits that have nothing besides lights on them. But when lights share circuits with other devices, lights can often bear the brunt of the larger devices' power demands.
Dishwashers, air conditioners, ceiling fans, bathroom exhaust fans, and televisions are just a few of the appliances that can interfere with the operation of a light that happens to share the circuit. When a very large draw—such as an A/C unit or a furnace—begins, any light on the circuit can flicker or lose brightness.
Troubleshooting a Flickering Light Bulb
- Loose Bulb: Loose light bulbs are fixed by first turning the bulb slightly counter-clockwise, then turning it clockwise again until tight.
- Loose Outlet: Outlets are solid-state devices and should not be repaired. Replace the outlet.
- Faulty Light Fixture: With ceiling lights, the solution is usually not to repair the light fixture but to purchase and install a new fixture. Floor and table lamps can be rewired.
- Faulty Dimmer: Faulty or damaged dimmer switches should be removed and discarded, then replaced with new dimmer switches.
- Mismatched Dimmer: Remove the old dimmer switch. Purchase a dimmer switch that is rated for LED lights and install it.
- Loose Wiring: Loose wiring can be fixed by methodically testing every connection point. If the connection is solid, it can stay. If it is loose, it can be re-connected.
- Power Demands: Removing the light fixture from the overloaded circuit and creating a fresh circuit is often the cure to this problem.
How to Diagnose a Flickering Light Bulb
- Diagnose the cause of a flickering light bulb by starting with the easiest repairs and working toward the more difficult repairs. No matter what else you do, you'll always want to start by tightening the light bulb.
- Check the connection for floor and table lamps. The plug should stay firmly in place with a gentle tug.
- With faulty light fixtures, remove the light cover and lightly tap the side of the fixture with your knuckles. The light should not flicker. If it does, the fixture needs to be replaced.
- Faulty dimmer switches can be tested by temporarily replacing the dimmer switch with a simple single-pole non-dimmable light switch. If the light works fine with this switch, then the problem lies with the dimmer switch.
- Mismatched dimmer switches are difficult to identify by looking at the switch or even the metal housing. Find your switch online and check its specs for compatibility. If in doubt, replace the switch with a compatible one.
- Loose wiring is hard to diagnose. Sometimes, wiring is so loose at switches that vibration from your hand can cause the lights to flicker. Otherwise, you'll need to hunt through the electrical boxes or have an electrician do this for you.
- Flickering bulbs caused by power demands announce themselves when the other, larger device turns on. If your lights flicker after the air conditioner or dishwasher turn on, that's probably the cause.
When a Flickering Light Bulb Signals a Serious Problem
The causes of flickering light bulbs can run the gamut from something as simple as a loose bulb on up to serious issues stemming from overloaded circuits or poor wiring connections along the circuit pathway. Flickering light bulbs can be signs of serious problems that can affect your home and your safety.
How to Install a New Light Fixture
When the underlying cause of the flickering light bulb is a faulty light fixture, replacement is a simple matter.
Watch Now: How to Install a Light Bulb Fixture
Equipment / Tools
- Voltage tester
- Cordless drill or screwdriver
- Wire stripper
- Light fixture
- Wire nuts
Turn off Circuit Breaker
Locate your electrical service panel (or breaker box), typically located in a hallway, downstairs, in a basement, in a mudroom, or in a garage. Turn off the circuit breaker that regulates the flow of electricity to the light fixture area.
Turning off the light switch alone is not considered safe practice for working with electricity. You must also turn off the circuit breaker.
Remove Light Cover
Remove the glass or plastic cover to the light fixture. In many cases, you only need to turn out three or four of the ribbed screws by hand. These screws are located on the side of the fixture. Set the cover aside.
Remove Fixture From Ceiling
Use the cordless drill or manual screwdriver to loosen the light fixture from the electrical ceiling box. Gently let the fixture drop to expose the electrical wiring. Be careful not to touch any of the wires yet.
Test for Electricity and Remove Wires
Turn on the voltage tester. First, test it out on a working electrical circuit. Then, standing on a stepladder, hold the voltage tester near all of the wires in the light fixture.
If all of the wires are confirmed to be dead (no electricity), unscrew the plastic wire nuts from the wires. To do so, hold a pair of wires in one hand while unscrewing the wire nut counter-clockwise with the other hand. When all of the wires are detached, remove the light fixture and set it aside.
Connect White Wires
Have an assistant help you as you connect the new light fixture with the wires in the ceiling box. Twist the white (neutral) wires of the light fixture clockwise onto the wires of the ceiling box. Then, twist an appropriately sized wire nut onto the twisted wire connection.
After the wire nut is attached, no bare wires should be exposed. If they are, remove the wire nut, slightly clip the end of the connection to shorten it, firm up the connection by twisting it again, and re-apply the wire nut.
Attach Black Wires
Attach the black (hot) wires of the light fixture with the black wires of the ceiling box. Do this the same way you connected the white wires.
Connect Ground Wires
Connect the bare copper or insulated green ground wire from the ceiling box to the paired wire of the light fixture. In some cases, the light fixture will not have a ground wire, so the ground wire from the ceiling box will attach directly to the metal body of the light fixture.
Attach Light Fixture to Ceiling Box
Press the wires into the ceiling box while simultaneously lifting the light fixture into place. By hand, push the screws through the body of the light fixture and into the matching holes of the ceiling box. After the screws have been threaded on, follow up by turning in the screws the rest of the way with the cordless drill or screwdriver. Make sure that the fixture is tight against the ceiling.
Install the bulb or bulbs into the light fixture. Be sure to consult the light fixture's instruction manual to prevent exceeding the wattage of bulbs. Attach the light cover again.
Turn on Electricity
At the electrical service panel, turn on the circuit breaker that controls the light fixture. Turn on the room's light switch, too. Leave the light on and observe it for signs of flickering.
When to Call a Professional
If you've investigated some of the simpler causes of flickering light bulbs to no avail, it's time to call in a qualified, licensed electrician.
The electrician can help you track down loose wiring connections. In the event of a mid-cable puncture by a nail or screw, the electrician can replace that cable for you. For power demand–related problems, an electrician can run an entirely new branch lighting circuit and wire the light into it.